A Cacophony of Causes
Although I do my share of fieldwork and backpacking, I am not a particularly athletic person. Nor do I partake of spectator sports. Thus I am not apt to use a sports metaphor. "Three strikes and you're out," however, seems fitting imagery to express my conclusion about what likely happened at the end of the Cretaceous.
Actually, with all the politically motivated attention to crime, the phrase has taken on another, more foreboding meaning--that of ridding society of career criminals by imprisoning them for life. It is more in this sense that I use the phrase when referring to extinctions at the K/T boundary and, more precisely, to the three major environmental events that may have coincided to cause these extinctions--marine regression, extraterrestrial impact, and massive volcanism. None of these three agents of biological destruction is, in my view, sufficient by itself to be crowned the sole cause of extinctions at the K/T boundary. Were all three necessary, however, for the pattern of extinctions evident at the K/T boundary?
After sorting through the disparate strands of evidence, I have come to conclude that marine regression and an impact are both implicated in the pattern of turnover at the K/T boundary, but I am less certain about volcanism. My uncertainty here is not because I doubt the